Electric clock mechanism



Aug. 16, 1960 P. G.-GERHARD ELECTRIC CLOCK MECHANISM Filed May 28, 19 58 PAUL 6. GER/"MRO INVENTOR ELECTRIC CLOCK MECHANISM Paul G. Gerhard, Washington, D.C., assignor to the Umted States of America as represented by the Secretary of the Army Filed May 28, 19 58, Ser. No. 738,574

3 Claims. (Cl. 318-131) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention generally relates to a novel clock mechanism which can be used to eifect detonation of fuzes in land mines.

Military specifications require that clock mechanisms which are used in land mines be able to operate after very long periods of shelf life. Known prior art clock mechanisms do not always satisfactorily meet this requirement because their electrical contacts form oxides during storage and also tend to corrode or rust together. It is very desirable that these mechanisms operate with a minimum number of moving parts, thereby reducing the possibility of failure.

It is an object of this invention, therefore, to provide a clock mechanism which has a long shelf life and which operates with a minimum number of movable parts.

In a typical embodiment of the invention, this object is accomplished by a novel electrical oscillating clock mechanism, which incorporates in a simple and compact structure, a single oscillating electric contact member which is adapted to automatically provide a self-cleaning action simultaneously with the oscillating contact action necessary for operation of the electrical clock mechanism.

The specific nature of the invention, as well as other objects, uses, and advantages thereof, will clearly appear from the following description and from the accompanying drawing, in which:

Figure l is a plan view of the clock mechanism in accordance with this invention with the top of the clock housing removed.

Figure .2 is a right side elevation of Figure 1 showing the relative positions of the index and ratchet wheels.

Figure 3 is an enlarged view of the end of the wiping arm contacting an index wheel tooth.

In Figures 1 and 2 there is shown lower and upper plastic plates A, A forming the clock housing which has within it a battery 11 providing energy for the C magnet having opposed poles 10a. Contacts 13, 13a are attached to lead wires 28, 33 which form a coil 10b on the magnet 10 and can be electrically connected by depressing starting switoh 12 in the direction shown by the arrow. Hub 14a rotatably mounts balance Wheel 14 on shaft 15 which is secured to the lower plate A. Balance wheel 14 is mounted perpendicularly to the longitudinal axis of the poles 10a and centrally positioned with respect to the extermities of the poles. Attached to the hub 14a is soft iron bar armature 16 with its longitudinal axis intersecting the axis of rotation of the hub 14a. Hairspring 17 is also connected at 1711 to the hub 14a at one end, and to the lower plate A at the other end by means of pin 17a. The hairspring 17 is capable of winding and unwinding and normally restrains the balance wheel 14 from moving, keeping it in the position shown in Figure 1 where the longitudinal axis of the 2,949,571 Patented Aug. 16', 1960 ICC pallet arm 19. Pallet arm 19 is pivotally connected to the clock housing A by means of shaft 20 and has a spring 21 which is attached at 21a to the underside of the pallet arm 19 approximately midway between the pivot 20 and the spring end of the pallet arm 19. Spring 21 is flexible enough to bend from 21a and ride over the index teeth 22:: of index wheel 22 when the pallet arm is swung upwards as viewed in Figure 1. When the arm 19 is swung downwardly spring 21 abuts the underside of the arm and is capable of moving the teeth and rotating index wheel 22. Index wheel 22 is fixed to.

shaft 23, the latter being pivotally mounted to the clock housing A, A. rotates. Shaft 23 also has ratchet Wheel 24 and pinion '49 fixed thereto and capable of rotating with the shaft. Pinion 40 is adapted to drive any conventional clock gearing system which may be used to arm a mine fuze (not shown) in a manner which will be readily apparent to those skilled in the art.

Ratchet arm 25 engages with the teeth of ratchet wheel 24 and prevents a rotative movement of the ratchet and indexwheels as well as shaft 23 and pinion 40 in any direction other than that given to dinxe wheel 22 by pallet arm 19. Ratchet arm 25 is pivoted at pin 26 and urged towards the ratchet teeth by magnet '27.

Wiping arm 30 made of a noncorrosive metal such as stainless steel is positioned substantially tangentially to the periphery of the index wheel and engages the surfaces of teeth 22a of index wheel 22 with a curved end 30b tapering to a point (Figure 3). Pivot pin 31 is suitably insulated from, and secured to the lower housing plate A. Wiping arm 30 is urged against the teeth 22a which should also be made of a noncorrosive metal such as gold, stainless steel or nickel by spring 32, and the pressure which the spring exerts on the arm as shown by C in Figure 3 is adjustable by means of screw 34 in bracket 35. Lead wire 33 terminates to form a connection with portion 30a on arm 30 at 33a. Lead wire 28 terminates to form an electrical contact with shaftv 23 and serves to put the index wheel 22 in series with the wiping arm 30 is between two successive teeth ofthe index wheel 22 so that the circuit is open and the magnet 10 is not energized. When it is desired to arm the mine fuze, the starting switch 12 is momentarily depressed so that the battery 11 momentarily energizes the magnet 10. The armature 16 is attracted by poles 10a from the position shown in Figure 1 where it was held by hairspring 17. The eccentric pin 18 drives the pallet arm 19 upwards and the spring 21 rides over the index tooth 22 1 Clockwise movement of the index wheel in response to the wiping action accomplished by spring 21 in its upward movement on tooth 22a is prevented by ratchet arm 25 engaging the teeth of ratchet wheel 24. Since the starting switch is closed momentarily, the electromagnet is de-energized before the armature aligns with the poles 10a. Balance wheel 14 is adapted to have enough inertia to rotate a few degrees beyond the pole pieces 10a, and by so doing winds hairspring 17. Hairspring 17 then unwinds and causes the balance wheel to rotate back towards its original position as shown in Figure 1. The return of the armature causes the eccentric pin 18 to drive the pallet arm 19 downwards so that the spring 21 moves the tooth 22:1 counterclockwise Shaft 23 rotates when index wheel 22 driving the index wheel a distance approximately the same as that between the apexes of two adjacent teeth. At the same time the curved tapered end 30b of wiping arm 30 performs the dual function of cleaning and momentarily contacting the index wheel tooth 2211 by frictionally rubbing against the index wheel tooth as the index wheel rotates. Should the index tooth 22x1 have a film of foreign matter on its surface the scraping action of the wiping arm end 30b will remove it and insure reliable electrical contact be tween the wiping arm and the index wheel teeth.

When momentary contact between the tooth 222a and the wiping arm 30 occurs the circuit will be closed and battery 11 will again energize the coils b causing the armature 16 to swing towards poles 10a and thereby wind hairspring 17. As the index wheel 22 rotates it causes rotation of shaft 23 and gear 40 connected thereto. Gear 40 can then drive any conventional clock gear train for some predetermined rotation of the gear train, the predetermined rotation determining when arming of the fuze device should occur.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

1. An improved electric clock mechanism for use in a fuze comprising: a housing for said clock mechanism, a C magnet within said housing having aligned opposed poles, a balance wheel rotatably mounted by means of a concentric hub, said wheel having its center perpendicular to the longitudinal axis of said poles and centrally positioned with respect to the extremities of said poles, a bar armature connected to said wheel with its longitudinal axis intersecting the axis of rotation of said wheel, a pin on said hub positioned eccentrically with respect to the axis of rotation of said wheel, a pallet'arm pivotally connected to said housing and having a yoke end and a spring end, the pivotal connection being located between said yoke and spring ends, said yoke end being driven by said pin, an index wheel rotatably mounted to said housing by means of a concentric rotatable shaft, the pivot axis of said pallet arm and the axes of rotation of said hub and rotatable shaft being substantially parallel, said index wheel being provided with a plurality of outwardly extending tooth portions on its periphery, said spring end of said pallet arm adapted to strike said tooth portions and drive the index wheel in one direction only, a wiping arm having a curved, pointed end in wiping contact with said tooth portions, said arm being centrally pivoted to said housing the other end of said arm provided with a spring which engages a bracket in said housing and resiliently urges said pointed end of said wiping arm into perpendicular contact with said tooth portions, a wire coil on said magnet having first and second leads, the first lead end connected to said wiping arm between said pointed end and said spring, the end of said second lead contacting said rotatable shaft, a battery source connected to said second lead, said rotatable shaft, wiping arm, index wheel and battery being electrically connected in series by said leads, the periodic contacting between the wiping arm and successive index wheel teeth causing the battery to periodically energize and pulse said magnet, the scraping action of the pointed end of said wiping 4 arm at the same time serving to scrape foreign matter from said tooth portions, the pulsing of said magnet causing oscillation of said armature and hub, said oscil lation causing the eccentric pin connected to said hub to cyclically drive said pallet arm thereby driving said index wheel and said rotatable shaft.

2. An improved electric clock mechanism for use in a fuze comprising: a housing for said clock mechanism,

a C magnet within said housing having aligned opposed poles, a balance wheel rotatably mounted by means of a concentric hub between said poles, a bar armature connected to said wheel with its longitudinal axis intersecting the axis of rotation of said hub, an eccentric pin on said hub, a pallet arm pivotally connected to said housing and having a yoke end and a spring end, the pivotal connection being located between said yoke and spring ends, said eccentric pin adapted to drive said yoke, an index wheel rotatably mounted in said housing by means of a vertical rotatable shaft, the pivot axis of said pallet arm and the axes of rotation of said hub and rotatable shaft being substantially parallel, said index wheel being provided with a plurality of outwardly extending tooth portions on its periphery, said spring end of said pallet arm being adapted to strike said tooth portions and drive said index wheel only in one direction, a wiping arm having a curved, pointed end in wiping contact with said tooth portions, said arm being centrally pivoted to said housing, the longitudinal axis of said wiping arm being positioned substantially tangentially to the periphery of said index wheel, the other end of said arm provided with a spring which engages a bracket in said housing and resiliently urges said one end of said wiping arm into perpendicular contact with said tooth portions, a wire coil on said magnet having first and second leads, the first lead having an end electrically connected to said wiping arm, the end of said second lead contacting said rotatable shaft, a battery connected to said second lead, said rotatable shaft, wiping arm, index wheel and battery being electrically connected in series by said leads, the periodic contacting of the pointed end of the wiping arm by the index wheel teeth serving to clean said tooth portions and at the same time causing the battery to periodically energize said magnet, the periodic energizing of said magnet causing oscillation of said armature and hub, said oscillation causing the eccentric pin connected to said hub to cyclically drive said pallet arm so that said spring end is moved into engagement with said tooth portions of said index wheel thereby driving said index wheel and rotatable shaft.

3. The improvement as claimed in claim 2, wherein a toothed ratchet wheel is connected to said rotatable shaft so as to rotate therewith, a ratchet arm extending substantially radially into engagement with said ratchet wheel, said ratchet arm engaging teeth on said ratchet wheel and thereby limiting rotational movement of said shaft in one direction only.

References Cited in the file of this patent UNITED STATES PATENTS 1,175,610 Cove Mar. 14, 1916 FOREIGN PATENTS 804,241 France July 27, 1936 

